This invention relates to thermoplastic olefin (TPO) compositions with excellent flame retardant properties.
Thermoplastic olefin compositions are used in many applications, including automotive and footwear applications. A new emerging field is the use of these compositions for electrical applications, such as injection molded containers for electrical components and devices. These applications require that the composition have good flame retardant properties, as indicated by a UL 94 rating of “V-0,” which means that a test bar formed from the composition, self-extinguishes, in the vertical position, after a repeated exposure to a flame.
International Publication No. WO2008/07998 discloses compositions containing platy fillers. These compositions contain a propylene homopolymer, an ethylene/α-olefin interpolymer a platy filler, and a nitrogen source and a phosphorus source.
European Patent Application No. EP1081183A2 discloses compositions that contain fillers, such as glass fibers, and a flame retarding effective additive of at least one polyphosphate, a sulfur containing compound, catalyst and a nitrogen containing compound such as melamine. Polymers include those selected from the group consisting of polyamides, polybutylene terephtalate, polyethylene terephtalate, polypropylene, polyethylene, polystyrenics, polyurethanes and polyacrylics, polycarbonates, polyarylates, polysulfones, polyetherketone, polyetheretherketone, polyphenylene oxide, polyphenylene sulfide, epoxy resins and thermosets, and blends thereof. Additional fillers include mineral fibers, carbon fibers, aramide fibers, gypsum, wollastonite, and lignin-containing fibers.
U.S. Publication No. 2007/0299171 discloses a composition comprising a formulation based on a phosphinic acid salt and melamine derivatives. The composition can be used for producing articles used for electric or electronic connections.
U.S. Publication 2002/0155348 discloses a battery casing formed from a composition that contains a blend of a homopolymer, copolymer and ammonium polyphosphate. Other components include polyol, intumescent char-forming agent, and melamine, which act as a blowing agent. Alternatively, the battery casing contains a polymer composition containing a halogen-containing fire-retardant component and a polypropylene component.
Additional compositions are described in EP1719800A1.
There remains a need for thermoplastic polyolefin compositions that have excellent flame retardant properties. Also, there is a need for such compositions that have high filler loadings to meet tensile properties, such as flexural modulus. Moreover, there is a need for highly filled compositions that contain fillers that do not interfere with the flame retardant properties of the flame retardants. These needs have been met by the following invention.